1. Field of the Invention
Note that in this specification, a semiconductor device refers to a semiconductor element itself or a device including a semiconductor element. As an example of such a semiconductor element, for example, a thin film transistor can be given. In addition, a semiconductor device also refers to a liquid crystal display device.
2. Description of the Related Art
In recent years, semiconductor devices are indispensable to human life. A semiconductor element such as a thin film transistor included in a semiconductor device is manufactured by forming a thin film such as a semiconductor film over a substrate, and processing the thin film into a desired shape. Such a manufacturing method is used for forming a liquid crystal display device (for example, a liquid crystal television).
An amorphous silicon film has been often used as a semiconductor film in a thin film transistor of a conventional liquid crystal television. This is because a thin film transistor formed using an amorphous silicon film has a structure relatively ease to form.
However, when the current circumstances of moving images (e.g., watching movies and sports in 3D) is taken into account, sharpness of moving images in a liquid crystal television using an amorphous silicon film is insufficient; thus, a thin film transistor which responds at high speed and has high carrier mobility has been developed. Accordingly, a microcrystalline silicon film has been developed (e.g., Patent Document 1).